1) Nucleon 2) The antiparticle of a neutron 
The antineutron is the antiparticle of the neutron with symbol {SubatomicParticle|Antineutron}. It differs from the neutron only in that some of its properties have equal magnitude but opposite sign. It has the same mass as the neutron, and no net electric charge, but has opposite baryon number (+1 for neutron, −1 for the antineutron). This is b...
[n] - the antiparticle of a neutron
noun the antiparticle of a neutron
an elementary particle having no charge and having a mass and spin equal to that of the neutron but with magnetic moment opposite to that of the neutron; the antiparticle of the neutron.